*{box-sizing:border-box;}

body {background-color: black;}

#container {display:flex;
  margin:auto;
  width:800px;
}

.piano {width:100px;
  height:600px;
  border:2px solid;
  border-radius: 15px;
  padding-top:525px;
  text-align:center;
  font-size:36px;
  font-family:'arial black', arial, sans-serif;
  background-color:white;
}

.pressed {background-color:grey;}